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2 Pure SubstancesMaterials are made of a pure substance or a mixture of substancesA pure substance, or substance, is a type of matter with a fixed compositionA substance can either be an element or a compoundex. Helium, Water, Salt

3 Elements All substances are built from atomsIf all atoms in a substance have the same identity, the substance is an elementEx. Copper, gold, silverAll of the elements are found on the Periodic Table

4 Compounds Two or more elements can combine to form a compoundA compound is a substance in which the atoms of two or more elements are combined in a fixed proportionEx. Table Salt- Compounds have properties different from the elements that compose them- Definite Ratio- Can only be decomposed into elements by chemical rxns. (can’t physically separate them)

5 MixturesA mixture is a material made up of two or more substances that can be easily separated by physical meansComponents retain their own identifying propertiesNo definite compositionCan be separated by dissolving, filtering, evaporating, magnetics, screening, etc.Mixtures can either be heterogeneous or homogeneous

6 Heterogeneous mixturesA heterogeneous mixture is a mixture where different materials can be distinguished easilySome are easily seen while others are notEx. Pizza

8 SolutionsSolution - A homogeneous mixture in which the components are close to the size of individual particles of the substance and are too tiny to be seen with a microscope and will never settle to the bottom of a containerSolutions remain constantly and uniformly mixed

10 Mixtures can occur between and among all phases of matterGas/gas (air)Gas/liquid (oxygen in water)Liquid/liquid (alcohol in water)Liquid/solid – (sugar in water)Solid/solid – (alloy such as steel)Ex. The addition of 10-30% chromium creates stainless steel

11 Physical PropertiesA physical property of a substance is any characteristic of a material that you can observe without changing the identity of the substances that make up the materialPhysical properties can be observed directly of measured with a toolExamples of physical properties include boiling point, color, shape, size

12 Boiling/Freezing/Melting PointsBoiling/Melting/Freezing points refer not to the phase change itself, but to a measurement: the temperature at which these changes occurPhysical properties because the composition of a substance doesn’t change during phase change or when one measures temperature to determine these points

13 Density Density is the mass of a substance per unit volumeThe density of a particular substance (under constant conditions) is always the same, regardless of sample sizeThe composition of a substance doesn’t change when one measures mass and volume to find density -> physical propertyDensity = massvolume

14 SolubilitySolubility – the maximum amount of a solute (substance being dissolved) that can dissolve in a given volume of solvent (the dissolving medium) at a particular temperature and pressureThe components of solutions do not chemically combine to form a new substance, therefore solutions are composed of two substances which each retain their own properties -> physical property

15 Viscosity Viscosity is a measure of a material’s resistance to flowHigh viscosity fluids take longer to pour than low-viscosity fluidsThe composition of a fluid doesn’t change when it is poured -> physical property

16 Electrical ConductivityA solid is either an electrical conductor or insulator based on its ability to complete an electric circuit

17 Physical Changes ReviewAny observations/measurement made WITHOUT changing the composition of the matterColorTextureDensityOdorSolubilityMelting/boiling point (Any Phase Change)

18 Physical Change A change in size, shape, stateIdentity of the element/compound does not changeChange in Shape/SizeAluminum Foil cut in halfChewing your foodChange in StateRubbing alcohol evaporates in your handJuice box freezes in freezer

19 Signs of a Physical ChangeAny phase change Change in energy of the particles What you started off with is what you end up with chemically

20 Chemical PropertiesA chemical property is a characteristic of a substance that indicates whether it can undergo a change that will alter the composition of the substanceA change of one substance to anotherEx. The capacity to oxidizeThe capacity to corrodeCombustibility

21 Chemical ChangesSubstance(s) present at the beginning of the reaction are changed into something new.You BREAK or MAKE bonds!!The change can’t be undone

24 The Capacity to OxidizeA substance combines with oxygen to form a new substance with new propertiesThe new substance formed is a combination of the atoms of the original substance and oxygenProperties of a substance change during the process of oxidation

25 Combustibility Combustion is a special type of oxidationWhen combustion occurs, a substance combines with oxygen to form a new substance with new properties in a process that releases heat and light

26 The Capacity to CorrodeCorrosion – the process by which metals naturally combine with oxygen, sulfur, or other nonmetalsWhen corrosion occurs, the new substance that is formed is a combination of a metal and a nonmetalThe properties of a substance change during this process

27 Conservation of MassThe mass of all substances present before a chemical change equals the mass of all the substances that remain after the change (this will be more important later)Ex. A burning log, even though ashes are left and weigh less, if you could collect all the gases lost during the burning and measure their masses too, mass would be conserved

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